There is carried out hemming working for folding to bend a flange constituted by erecting a hem portion of a panel in a direction of an inner side of the panel with regard to hem portions of a bonnet, a trunk, a door and a wheel house of an automobile. As the hemming working, there can be pointed out roll hemming working of positioning to hold a panel above a die and folding to bend a flange at an end portion of the panel while pressing a roller thereto. In roll hemming working, a fold-to-bend angle is large, and therefore, there is a case in which working is carried out by being processed by a plurality of stages of steps of preparatory bending (or prehemming) and finish bending (or regular hemming) in consideration of a fold-to-bend accuracy.
As an apparatus for rolling hemming working, there is proposed an apparatus of fixing a die to a work by clamps arranged at a plurality of portions thereof (refer to, for example, JP-A-06-297046).
It is preferable to form a shape of a work without error to be aligned to a shape of a die, and when the work is constituted by one sheet of a panel member as in a door panel or a bonnet, portions to be worked are few and an error is difficult to be brought about. On the other hand, when the work is constituted by a box structure or the like constituted by welding a plurality of plate members as in a white body, there is a tendency of bringing about a distortion by heat of welding and a clearance is liable to be brought about at an interval from a die.
Even when a clearance is brought about between a work and a die, in a case in which the work is constituted by one sheet of a panel member, the panel member is temporarily bent to follow a shape of the die in rolling a roller relative to the panel member, and therefore, a portion to be hemmed is pertinently bent.
However, when the work is constituted by a box structure or the like, the work is highly rigid and bending is not produced, and therefore, a die is not effectively operated at a portion having a clearance and there is a concern of bringing about a wrinkle in a wavy shape at a portion to be hemmed. Further, when a press force of a roller is excessively increased to eliminate a clearance, the work is distorted.
Hence, it is an object of the invention to provide a hemming working method and working apparatus capable of firmly bringing a work into contact with a die, folding to bend a portion to be hemmed by a pertinent shape and preventing a distortion or a deformation of the work even when the work is constituted by a shape having an error relative to the die.
Further, as hemming working, there is proposed a method of carrying out hemming working by setting a work to a die provided at an exclusive space for carrying out an exclusive step and rolling a unit held at a front end of a robot along a flange (refer to, for example, JP-A-07-060370, JP-B2-2924569).
Meanwhile, in an automobile industry in recent times, it is desired to develop a product in a short period of time and fabricate a number of vehicle kinds at the same time and it is desired to shorten a hemming working time period by making a rolling speed of a roller for hemming working high from a view point of further promoting a productivity and shortening a cycle time.
However, according to the method described in JP-A-07-060370, a movement of a press roller constituting a roller for hemming working in hemming working is controlled only by a movement of a robot, particularly in preparatory bending, it is difficult to regulate an attitude and a press force of the press roller, for example, when a rolling speed of the press roller is made to be high, there is a concern of bringing about a working failure in which a flange is excessively folded to bend or wavy.
Further, according to the method described in JP-B2-2924569, although there is provided a guide portion of guiding a direction of rolling a roller for hemming constituting a roller for hemming working, a groove for guiding is constituted only by one streak, and therefore, different hemming rollers need to be used in preparatory bending and finish bending, and an extraneous time period is required for interchanging the rollers. Further, when the rolling speed of the roller for hemming is made to be high, a moving locus and a teaching locus (a guiding direction of a guide groove) of a robot are considerably shifted from each other, a friction between the guide portion and the guide groove is increased, depending on cases, there is a concern that the guide portion rides over the guide groove. Further, the roller for hemming and the guide portion are coaxially and integrally constituted, and therefore, when the guide portion rides over the guide groove, the roller for hemming is floated from the flange and there is a concern of bringing about an extreme working failure.
Further, according to the method described in JP-B2-2924569, a roller shaft for coaxially and integrally supporting the roller for hemming and the guide portion is constituted to be able to move up and down while maintaining a horizontal state by a universal joint, and in positioning before hemming working, the guide portion can be moved in a lower direction to be installed at the guide groove by a pinching cylinder for moving the roller shaft up and down. However, in hemming working, the roller shaft is fixed to a wrist portion of the robot by a press force of the pinching cylinder, and therefore, as described above, the guide portion rides over the guide groove by increasing a friction between the guide portion and the guide groove, the roller for hemming is floated up from the flange, and there is a concern of bringing about an extreme working failure.
Hence, it is an object of the invention to provide a hemming working method and a hemming working apparatus capable of making a roller follow along a flange at a high speed and accurately by flexibly supporting the roller in hemming working.
Further, it is an object of the invention to provide a hemming working method and a hemming working apparatus capable of swiftly positioning a roller before hemming working even in a constitution of flexibly supporting the roller in hemming working as descried above.
Further, it is an object of the invention to provide a hemming working apparatus capable of making a roller follow along a flange at a high speed and accurately.
When hemming working is carried out, it is convenient to leave a portion of a flange to be erected. However, according to rolling hemming working of the background art, a roller is vertically pressed to a flange to be folded to bend at a work start portion, and therefore, a change in a stress and a shape at a boundary portion of a portion of leaving a portion of the flange to be erected and a fold-to-bend portion and there is a concern of bringing about a wrinkle.
Hence, it is an object of the invention to provide a hemming working method and working apparatus capable of realizing a gradual change in a shape and preventing a wrinkle, a crack or the like from being brought about by adjusting a fold-to-bend angle of a flange in accordance with a portion to be worked.
Further, it is an object of the invention to provide a hemming working method and working apparatus capable of bringing a moving die into contact with a work by a pertinent attitude.
Further, there is a case in which a panel member of a door or the like of a vehicle is constituted by combining an inner panel and an outer panel. When the inner panel and the outer panel are combined, the inner panel is pinched by carrying out hemming working of folding to bend a flange of the outer panel, thereafter, spot welding is carried out further to ensure a bonding strength.
In order to firmly carry out spot welding, a projection may be provided at the inner panel, the flange may be folded to bend such that the flange is brought into contact with an upper portion of the projection, thereafter, spot welding may be carried out by pressing a welding electrode to press the projection from a surface of the flange. Thereby, a current is concentrated on the projected portion to achieve firmly melting and a welding stress is promoted.
In this case, when the projection is pressed to crush by a back face of the flange in folding to bend the flange, an effect of concentrating the current in spot welding is reduced, and therefore, there is desired a measure of folding to bend the flange while leaving the projection.
In order to prevent a projection or the like of the panel member from being pressed to crush, there is proposed a method of rolling a roller while following recesses and projections by using a hemming roller a surface of which is brought into a gel state (refer to, for example, JP-Y2-2561596).
Further, in hemming working, when a flange is folded to bend in steps by being divided by a plurality of times, a highly accurate fold-to-bend portion is provided, which is preferable. The applicant has proposed a method of carrying out hemming working by being divided at least by two times in JP-A-2005-349471 or the like.
Meanwhile, according to the hemming roller described in JP-Y2-2561596, although an entire face thereof is constituted by a gel member and can follow a recessed and projected portion of a projection or the like, also other portion is pressed by way of the gel member, and therefore, a sufficient press force is not achieved. Further, the gel member repeats deformation at each time of riding over a projection or the like, and therefore, service life thereof is shortened, which is not practical.
Hence, it is an object of the invention to provide a hemming roller capable of folding to bend a flange without crushing a projection provided at a panel member, a roll hemming method, and a weld structure welding a panel worked by the method with high strength.
Further, JP-Y2-2561596 describes a hemming working apparatus including a guide roller for increasing a press force in hemming and providing a guide portion with which the guide roller is engaged to a die mounted with a work.
Further, JP-B2-2579530 discloses technical thought in which hemming working by a work roller is carried out at a linear portion of a work, and hemming working is carried out by a forming die at a corner portion having a small radius of curvature of the work.
Meanwhile, a bonnet, a trunk and a door or the like of an automobile as described above normally includes a corner portion having a small radius of curvature.
When the above-described corner portion is worked by the apparatus described in JP-Y2-2561596, it is necessary to constitute the guide portion by a shape comprising a small radius of curvature to be along a shape of the corner portion.
Then, it is difficult for the guide roller to follow the shape of the guide portion provided at the corner portion, there is a concern of bringing about derailing from the guide portion or biting the guide portion or the like, as a result, it is difficult to accurately make the work roller follow along the shape of the work.
Further, according to the method of JP-B2-2579530, it is necessary to prepare a plurality of forming dies for carrying out hemming working of corner portions of respective shapes (kinds) of works. Therefore, there poses a problem that a general purpose performance of an equipment is low and cost is increased.
Hence, it is an object of the invention to provide a hemming working method and a hemming working apparatus capable of making a work roller accurately follow even a portion having a radius of curvature of a corner portion or the like of a work. Further, it is an object of the invention to provide a hemming working method and a hemming working apparatus having a high general purpose performance of an equipment and capable of reducing cost.
FIG. 107A and FIG. 107B are views for explaining a basic principle of a roller hemming method according to a related art. (The related art is disclosed in, for example, JP-B-07-090299.) As shown by FIG. 107A, a rolling hemming apparatus 8100 is constituted by a lower die 8102 provided with a guide face 8101 and a flat roller 8104 rotatably supported by a robot hand 8103.
An outer panel 8107 having a flange 8106 is mounted on the lower die 8102, and an inner panel 8108 is mounted on the outer panel 8107. Further, the flat roller 8104 is rotated while being in line with the guide face 8101 to fold to bend the flange 8106 indicated by an imaginary line by about 45° up to a position indicated by a bold line. The step is referred to as a tackedly bending step or a primary bending step.
Next, as shown by FIG. 107B, a direction of the flat roller 8104 is changed by the robot hand 8103. Further, the flange 8106 indicated by an imaginary line is completely folded to bend up to a position indicated by a bold line. The step is referred to as a regular bending step or a secondary bending step.
FIG. 108B is a view for explaining a problem of the rolling method of the related art. As shown by FIG. 108A, assume that the work 8110 is a bonnet in which a front hem portion 8111 and a rear hem portion 8112 are bent. After the primary bending step, a front end portion 8115 of a flange 8113 becomes remoter from a bending center 8116 than a base portion 8114 of the flange 8113. That is, when a radius of the base portion 8114 is designated notation R1 and a radius of the front end portion 8115 is designated by notation R2, R1<R2. As a result, a peripheral length of the front end portion 8115 becomes larger than a peripheral length of the base portion 8114.
A similar peripheral length difference is present also at a guide face 8120 shown in FIG. 108B. When a radius of one hem (which is proximate to the bending center) 8121 of the guide face 8120 is designated by notation R3 and a radius of other hem 8122 is designated by notation R4, R3<R4. As a result, a peripheral length of the other hem 8122 becomes larger than a peripheral length of the one hem 8122.
When a flat roller 8123 is rotated without being slipped relative to the one hem 8121, a slip is necessarily generated between the other hem 8122 and the flat roller 8123.
A lower die 8124 including the guide face 8120 is constituted by hard steel and also the flat roller 8123 is constituted by hard steel. Therefore, at least one of the guide face 8120 and the flat roller 8123 is worn, and it is difficult to continue hemming working.
Therefore, the method of JP-B-07-090299 is not applicable to hemming working constituting an object by the work 8110 in which the front hem portion 8111 and the rear hem portion 8112 are bent.
Hence, it is a problem of the invention to provide a roll hemming technology preferable for a work a hem portion of which is bent.
FIG. 109 is a view for explaining a basic constitution of other related art. A hemming apparatus 9100 is constituted by guide cylinders 9103, 9103 fixedly provided at a support member 9102 attached to a front end of a robot arm 9101, slide shafts 9104, 9104 slidably guided to be supported by the guide cylinders 9103, 9103, sliders 9105, 9105 fixed to the slide shafts 9104, 9104, a cylinder 9106 coupled to the sliders 9105, 9105 and fixedly provided to the support member 9102, a hemming roller 9107 axially supported rotatably by the sliders 9105, 9105, a guide roller 9108 axially supported by the support member 9102, a guide rail 9111 for preparatory bending for guiding the guide roller 9108 and provided to a lower die 9109 to be inclined in a lower direction, and a guide rail 9112 for regular bending for guiding the guide roller 9108 and provided to the lower die 9109 vertically in a lower direction.
First, the guide roller 9108 is engaged with the guide rail 9112 for regular bending. Thereby, the hemming roller 9107 is disposed in a horizontal direction. Next, by operating to move back the cylinder 9106, regular bending working of constituting a pinched state is carried out by folding to bend an end hem 9114 of a lower side sheet 9113 which has been preparatorily bent by 45° over an end hem 9116 of an upper side sheet 9115. Hems of the lower side sheet 9113 and the upper side sheet 9115 can be connected thereby.
Meanwhile, the guide roller 9108 is constituted by a shape similar to that of a flanged wheel, and therefore, when the guide rail 9112 for regular bending is bent abruptly to some degree or more, the guide roller 9108 is derailed. Therefore, the hemming apparatus 9100 of the related art of FIG. 109 is applicable only to an end hem 9114 gradually bent in a head and tail direction of the drawing.
Further, abrupt bending can be reread as “large radius of curvature” and gradual bending can be reread as “small radius of curvature”. A radius of curvature is an inverse number of a radius. A work of a bonnet or the like of a vehicle includes corner portions having large radii of curvature at four corners thereof. Such a work cannot be worked by the hemming apparatus 9100.
FIG. 110 is a view for explaining a basic constitution of still other related art. A hemming forming apparatus 9200 is constituted by a jig 9203 for receiving an outer panel 9202 mounted with an inner panel 9201, an articulated robot 9205 mounted on a conveyor apparatus 9204 arranged in a side direction of the jig 9203, a roller holder 9207 attached to a front end of a robot arm 9206 of the articulated 9205, a forming roller 9208 attached to a front end of the roller holder 9207, die driving apparatus 9209 respectively arranged at vicinities of four corner portions of the jig 9203, and forming dies 9211 respectively attached to the die driving apparatus 9209.
Whereas the forming roller 9208 is run by being pressed from an upper side substantially at a linear portion having a small radius of curvature, by pressing to form the four corner portions having large radii of curvature respectively by the forming dies 9211, hemming working can be finished by folding to bend a fold-to-bend portion provided to the outer panel 9202 to the inner panel 9201.
That is, according to the hemming forming apparatus 9200 of the related art of FIG. 110, the linear portion of the work is worked by the forming roller 9208, and the four corner portions of the work are worked by the forming dies 9211. 4 pieces of the forming dies 9211 are needed, and therefore, the hemming forming apparatus 9200 becomes expensive. As described above, according to the related art of FIG. 109, hemming working is difficult for the portion having a large radius of curvature, and according to the related art of FIG. 110, although hemming working of the portion having the large curvature can be carried out, the hemming apparatus becomes expensive.
Hence, it is a problem of the invention to provide a roller hemming apparatus which can carry out hemming working of a portion having a large radius of curvature and inexpensive.